SSinister11x

My 96 SS just got a pair of Long tube headers and I deleted my Cats. I've heard of oxygen sensor simulators? But I was wondering could I just forget about the secondary sensors and leave em out? I know this will throw a code but will it mess with performance or anything?? I can Live with a code.

rv93

if youre ok with having your check engine light on, then theres nothing to be worried about. just make sure you get your codes read every once in a while, in case something shows up, since your check engine light wont be able to warn you.

SSinister11x

Awesome, thanx man. yeah my indicator light is busted anyway. I scan the car once a week it seems like just to be safe.

6SpdLT1Z

There will be no performance changes by removing/deleting the rear o2 sensors. You can either remove them and deal with the SES light (at least on OBD-II cars, not sure about OBD-I) or you can buy some simulators or have them tuned out. I had mine tuned out.

I am also running Long Tubes with a ORY.

Injuneer

OBD-I does not have after-cat O2 sensors.

Mr_Bad_Ratchet

I thought unexpected O2 readings, like a no sensor open (whether pre or post CAT) will turn on SES light AND cause PCM to go into open loop operation. That would cause major performance issues.
Also post CAT O2 location is critical to correct PCM operation.

rv93

sorry, but youve been misinformed. the sole purpose of the 2nd set of o2 sensors is to measure the efficiency of the cats. if they read less oxygen than the first set, everything's happy. if they read the same, the PCM turns on the SES light, and continues doing its job. it does not impact performance in any way

Mr_Bad_Ratchet

So you're saying the SES light on for an emissions fault would not cause open loop if it's a post cat o2? Would it be correct to say the my theory only applies to pre cat O2 sensors then?
I was also told that generically speaking only an emissions related fault code would cause the SES light to stay on.

Back to the original question. It sounds like it would be easy to "trick" the PCM into dealing with no post cat O2's without disabling the SES light.

Mr_Bad_Ratchet

rv93, thanks for inspiring me to search for information.

I did a google on this subject and found this website about o2's and cats. Very enlightening.
http://www.12v.org/engine/index.php?section=hw&sm=o2
The relevant quote, as you said... "The oxygen sensors downstream of the catalytic converters do not have any part in this process; they only monitor the function of the catalysts."

rv93

youre actually correct in thinking that the SES light generally deals with emissions related problems. there are codes that can be thrown for other reasons, but its main goals is to keep emissions in check. also, yes, it should be pretty easy to tune out the 2nd o2 sensors. ive never done it though.

6SpdLT1Z